Etiological Profile of Macrocytic Anemia in Patients Presenting to a Tertiary Care Hospital

A bstract Background: Macrocytic anemia is a common hematological finding with a wide range of causes, from nutritional deficiencies to systemic illnesses and bone marrow disorders. Mean corpuscular volume (MCV), routinely reported by automated blood analyzers, provides useful clues to the underlying etiology. Objectives: To study the etiological spectrum of macrocytic anemia and evaluate the usefulness of MCV in differentiating megaloblastic from nonmegaloblastic causes. Materials and Methods: This was a cross-sectional study that included 92 adult patients with anemia and MCV >100 fL who presented to the Departments of Medicine and Hematology between January and December 2024. Clinical features, hematological and biochemical parameters, vitamin B12 and folate levels, thyroid function tests, and bone marrow examination were analyzed. Based on etiology, patients were classified as having megaloblastic or nonmegaloblastic anemia. The diagnostic performance of MCV for identifying megaloblastic anemia was assessed using receiver operating characteristic (ROC) analysis and Youden’s J statistic. Results: Of the 92 patients, 38 (41.3%) had megaloblastic anemia and 54 (58.7%) had nonmegaloblastic causes. Besides megaloblastic anemia, common etiologies included chronic liver disease (19.6%), autoimmune hemolytic anemia (14.1%), aplastic anemia (7.6%), and myelodysplastic syndrome (5.4%). A vegetarian diet was significantly associated with megaloblastic anemia, whereas alcohol use was more frequent in nonmegaloblastic cases. Mean MCV was significantly higher in the megaloblastic group (118.0 ± 11.6 fL) than in the nonmegaloblastic group (109.8 ± 10.4 fL; P < 0.001). Elevated lactate dehydrogenase (LDH) and low haptoglobin supported ineffective erythropoiesis in megaloblastic anemia. MCV did not correlate with the degree of vitamin B12 deficiency, whereas hemoglobin showed a stronger relationship with B12 levels. ROC analysis demonstrated good diagnostic accuracy of MCV for detecting megaloblastic anemia. Conclusion: Megaloblastic anemia remains the leading cause of macrocytic anemia. Higher MCV values, combined with LDH and vitamin B12 levels, can help guide focused evaluation, particularly in resource-limited settings.